Charlotte , North Carolina -LRB- CNN -RRB- -- Republicans got first serve in their convention last week . Can Democrats break serve , or will the presidential race go to a tiebreaker in November ?

Here are five things to watch for at the Democratic National Convention :

1 . New man on the big stage -- Most Americans have never heard of the mayor of San Antonio . They will after Tuesday night when Julian Castro becomes the first Latino to give the keynote address at a Democratic convention . Past keynote speakers such as Bill Clinton and Barack Obama made it to the White House . Maybe that 's raising too many expectations for Castro , but his speech will be looked upon the same way .

2 . 2016 contenders -- Sen. Marco Rubio of Florida and vice presidential nominee Paul Ryan gave blockbuster speeches at the Republican convention in Tampa , Florida . New Jersey Gov. Chris Christie 's keynote address did n't go over as well . All three could make bids for the GOP presidential nomination in 2016 if Mitt Romney does n't win in November . So which Democrats are waiting in the wings ? Govs. Martin O'Malley of Maryland , Brian Schweitzer of Montana and John Hickenlooper of Colorado all have an opportunity in Charlotte .

3 . Turncoats -- Is Charlie Crist the Artur Davis of this convention ? Davis , the former Democratic congressman from Alabama who seconded Obama 's nomination four years ago , had a high-profile speech at the Republican convention . Now it 's Crist 's turn . What will the former Republican governor of Florida , who could possibly run for his old office as a Democrat , say when he gets in front of the podium in Charlotte ?

4 . What will Bill Clinton say ? -- There 's probably more anticipation , and questions , around the former president 's Wednesday prime-time address . Once former adversaries when Hillary Clinton was running against Obama , Bill Clinton has become one of Obama 's strongest advocates . But the big question is what will Clinton say when he nominates Obama for re-election Wednesday ? Obama campaign officials said they have n't seen Clinton 's speech yet , but they said they are `` not worried '' about what he 'll say .

5 . The ticket -- The traditional role of running mate is to be the attack dog . Will Vice President Joe Biden slam Romney as much as Ryan attacked Obama ? And how much of what the president will say in his acceptance speech is a defense of his first term and how much is an outline of what he wants to do over the next four years ?

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San Antonio Mayor Julian Castro will give the keynote address

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Possible 2016 contenders , many of them governors , will be on display

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Former Florida Gov. Charlie Crist takes his shot at the GOP

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Anticipation is high for former President Bill Clinton 's Wednesday night address